Method for treating paper insulation material in the manufacture of paper insulated electric cables



Feb. 25, 1941. c. F. PRQOS 2,233,298 METHOD FOR TREATING PAPER INSULATION MATERIAL IN THE MANUFACTURE OF PAPER INSULATED ELECTRIC CABLES Filed July 2, 1958 INVENTOR BY M y ATTORNEYS UNITED STATES PATENT Fries METHOD roa TREATING mesa HNSULA- from paper to be employed in the manufacture of.

TION MATERIAL IN THE ACTURE MANUF OF PAPER INSULATED ELECTRIC GABLES Cornelis Frederik Proos, The Hague, Netherlands Application July 2, 1938, Serial No. 217,223

In the Netherlands July 13, 1937 V 4 Claims. (CI. 34-24) The present invention relates to methods of substantially decreasing or removing moisture paper insulated electric cables.

An important objective sought in the manufacture of electric cables, and particularly hightension electric cables, is the production of a cable wherein dielectric losses are substantially minimized; indeed, the degree of attainment of this characteristic is commonlyused as a basis for judging the quality of the cable. I

In paper insulated cables, the dielectric losses of the cable itself depend largely upon the degree of dielectric losses of the paper insulation, and the said losses inthe latter depend partly upon the. moisture content of the P 41 11. By minimizing the moisture content of the paper, the dielectric losses of said paper, and, hence, of the cable itself, are appreciably reduced.

An important object of the present invention is the provision of an improved method for substantially removing the moisture from paper used in manufacturing paper insulated electric cables whereby to produce a more emcient and, hence, a higher quality of cable.

One means heretofore employed forjremoving the moisture from the paper insulation has been to subject the paper-wrapped cables to a drying process. It is obvious, however, that as the paper layer of insulation is increased on various types of cables, it becomes increasingly difficult to disperse the moisture from the insulation, so that where a thick layer of paper is employed on hightension cables where substantial dielectric losses would be most troublesome and most dimcult to prevent, the said process of drying the paperwrapped cables is least eifective for its intended purpose. Such drying process may be quite'effective as to cables having only a thin layer of paper insulation. but in such cables the dielectric losses are of relatively little concern. The said drying process, heretofore employed, is, thus, least eifective where drying is most needed and most effective where drying is leastneeded.

The present invention may be understood by reference to the following description and to the accompanying drawing, in which:

Figure 1 is a verticalsectional view oi a device which may be employed 'for heating rolls.

of paper, and

in; roll.

Paper, intended for use for the insulation of cables, is carried in relatively large supply rolls l which may be heated in any suitable manner;

The roll heating means, employed herein for purposes of illustration, may comprise a heating chamber or oven. 2, preferably having. double 5 walls 3, 3, with any suitable insulating medium 4 disposed therebetween.

The heating chamber may have a preferably foraminous false bottom or other support, indicated in broken lines in the drawing as at M for 10 supporting the rolls l. Air may be circulated in the said chamber, if desired, by means of any suitable circulating system,'which may comprise an intake port 5, an exhaust port 6 and suitable means for conducting air from port 6 to port 5, which'latter means may comprise a fan i and a heat transfer device 8 connected in series in a pipe connection 9 whereby to pump heated air into the chamber 2 through the port 5 and to exhaust it from the said chamber through the 20 port 6.

After av roll I has been sufliciently heated it may be removed from the heating chamber 2, then mounted, preferably in a horizontal position, upon a suitable stand In and unwound from 25 the heated roll I, onto anothersomewhat similarly mounted receiving roll la, all substantially as shown in Fig. '2. The heated paper, as it passes from the roll I, is exposed in and to air which is maintained in a. substantially unsaturated condition and at a lower temperature than the heated paper on the said roll. The conditions, just referred to, may be achieved in several ways. For example, the unwinding may be done in a room or compartment containing relatively cool, unsaturated air, or the paper may pass directly from the roll I, into a space or compartment containing such relatively cool unsaturated air. The degree of heating of the roll I and the temperature diflerence between the said roll and the air through which the said heated paper is passed, as it is unwound, should, of course, be sufllcient to vaporize and free the moisture from the paper. 7

If the paper is immediately 'rewound upon a roll Ia, as described, it is obvious that the outer layer or layers of paper on such roll will substantially prevent the escape of heat from, and the ingress of moisture to the underlying layers and hence, for a time the dried paper is kept heated and dry for future use.

It is also obvious that, shortly after the unwinding and winding operation already described, the paper on the roll la may be cut or otherwise processed and promptly incorporated as a part of an electric wire insulation. If this is done the paper on the roll I a may still be at a sufliciently high temperature that if it is again exposed to relatively cool unsaturated air in its course of movement to cutting or other processing machinery, any moisture which may not have previously been dispersed from the paper is given a further opportunity to vaporize and pass oiT.

It will also be understood that the paper may be passed from the heated roll I, directly to cutting or other processing machinery, being exposed to relatively cool unsaturated air in its a course of movement toward such machinery.

Furthermore, if a single heating of the roll I and unwinding of the heated paper therefrom in relatively unsaturated cool air should not sufiice to adequately dry the paper, the heating and unwinding, as aforesaid, may be repeated.

It should be observed that merely heating the roll of paper does not yield the results of the present invention, inasmuch as such heating, alone, provides no adequate evaporation of moisture and no adequate avenue of escape for such moisture from the relatively thick roll of paper. An important feature of the present invention is that, while the paper on the heated roll is still hot, it is drawn therefrom as a web and passed through, and efiectively exposed to, substantially unsaturated air at a lower temperature than the heated paper to a receiving roll or to a cutting or other processing machine, whereby vaporized moisture is effectively freed from the web.

It has been observed that cables provided with paper insulation which has been treated according to the present invention have very substantially lower dielectric losses than cables produced prior to this invention.

It should be understood that the advantages of the method herein described may be derived in various ways without departing from the spirit of the present invention.

I claim:

1. A method for. treating paper insulation material in the manufacture of paper insulated electric cables, which comprises heating a roll of paper and unwinding said paper from said roll, while in such heated condition, in substantially unsaturated air, whereby to vaporize and free the moisture from saidpaper.

2. A method for treating paper insulation material in the manufacture of paper insulated electric cables, which comprises heating. a roll of paper and unwinding said paper from said roll, while in such heated condition, in substantially unsaturated air of a lower temperature than the temperature of the said heated paper, whereby to vaporize and free the moisture from said paper.

3. A method for treating paper insulation material in the manufacture of paper insulated electric cables, which comprises heating a roll of paper and unwinding said paper from said roll, while in such heated condition, in substantially unsaturated air, whereby to vaporize 'and free the moisture from said paper, and thereafter substantially shielding said paper against communication with surrounding air whereby to substantially prevent ingress of moisture from such air into the paper and to substantially retain heat within said paper.

4. A method for treating paper insulation material in the manufacture of paper insulated eelctric cables, which comprises heating a roll of paper and unwinding said paper from said -roll, while in such heated condition, onto another roll, the paper, in its movement from the former roll to the latter roll, being passed through substantially unsaturated air, whereby to vaporize and free the moisture from said paper.

c'oRnEm's FREDERIK PROOS. 

